Magnetic recording media are basically heterogeneous structures comprised of both organic (polymeric) and metallic or ceramic materials. Under use, temperature variations of 40.degree. C. and humidity variations of 90% are not uncommon, yet the media must perform well regardless of the environment. In the case of video tape, the tape experiences both relative speeds of a few centimeters per second in tape transport and relative speeds of several hundred centimeters per second in video head velocity, yet the tape must be protected against wear at both speeds.
Lubricants are included in or coated on the magnetizable layer of the recording medium to protect against wear, and the demands placed on the lubricant are considerable. Known lubricants include silicones, liquid paraffins, straight chain fatty acids such as myristic acid, palmitic acid and stearic acid and fatty acid esters. With increasing amounts of fatty acid and liquid paraffin lubricants, the durability of the medium improves. However, amounts of lubricant which are too great can soften the coating, reducing its durability, and this may cause clogging of the recording or playback heads.
Still-framing in video recorders adds the problem of frictional heat which can damage the binder. In helical scan video recorders, tape motion is stopped, and the rotating heads scan a particular portion of the recorded material which is displayed on a television screen. The temperature generated in the contact area between the rapidly moving head and the tape can be in the order of several hundred degrees centigrade, and this may cause undue tape wear or the collection of debris on the head. Debris, as used here, means oxide or binder build-up on magnetic heads and tape guides. A stop motion test is used in the evaluation of video tapes.
There is a recognized need for a better lubricant system for helical scan video tapes. Current commercial systems are subject to variation both with respect to durability and stop motion. In addition, a decrease in signal-to-noise output (S/N) at low humidities is a continuing problem and must be improved.
Because disc drives are now being placed in factory, home, and other less protected and unconventional environments, media may face temperature extremes beyond the limits of old lubricant specifications. New lubricants are desired which are effective at low temperatures (e.g. about 5.degree. C.) where some prior art lubricants lose their effectiveness.